Dementia with Lewy bodies is a progressive neurodegenerative disorder characterized by cognitive decline, visual hallucinations, fluctuating cognition, and parkinsonism due to abnormal alpha-synuclein deposits (Lewy bodies) in cortical and subcortical neurons.

Dementia with Lewy Bodies (DLB)

Risk Factor	Mechanism / Explanation
Age	Single strongest risk factor; average onset ~75 years. Neuronal vulnerability to protein misfolding increases with age
Male sex	M:F = 4:1 ^[2]. Reason unclear; may relate to sex-hormone-mediated neuroprotection in females
Family history	Majority sporadic; familial forms associated with SNCA duplication/triplication ^[2]^[4]. GBA mutations (glucocerebrosidase) are the strongest genetic risk factor for sporadic DLB
GBA mutation	Encodes lysosomal enzyme glucocerebrosidase; impaired lysosomal degradation of α-synuclein → accelerated aggregation
APOE ε4 allele	Shared risk factor with AD; promotes amyloid co-pathology and may worsen cognitive decline in DLB
Other genetic loci	GBA, SNCA, APOE, BIN1, TMEM175, TPCN1, SCARB2 have all been implicated in genome-wide association studies ^[3]
REM sleep behaviour disorder (RBD)	Isolated RBD (iRBD) is now recognised as a prodromal α-synucleinopathy — up to 80–90% of patients with iRBD will convert to DLB, PD, or MSA within 10–15 years
Depression (late-onset)	Late-onset depressive disorders may be a prodromal feature of DLB

Genetic Overlap

The genetics of DLB overlap with Alzheimer disease and PD, suggesting that one genetic variation may have various phenotypes. ^[3] This explains why DLB often presents with mixed features and copathology.

4. Anatomy and Function (Relevant Neuroanatomy)

Understanding where Lewy bodies deposit explains the clinical features:

Brain Region	Normal Function	Consequence of Lewy Body Deposition
Deep cortical layers (anterior frontal, temporal lobes, cingulate, insula) ^[2]^[4]	Executive function, attention, emotional regulation, interoception	Early impairments in attention, executive function; apathy, anxiety
Occipital cortex / visual association areas	Visual processing	Well-formed visual hallucinations (VH); visuospatial dysfunction
Brainstem nuclei (substantia nigra, locus coeruleus, dorsal raphe, pedunculopontine nucleus)	Dopaminergic (motor), noradrenergic (arousal), serotonergic (mood), cholinergic (sleep/arousal)	Parkinsonism, cognitive fluctuations, mood disturbance, REM sleep behaviour disorder
Nucleus basalis of Meynert	Major cholinergic projection to cortex	Severe cholinergic deficit → cognitive impairment (often more severe than in AD, explaining better response to AChE inhibitors)
Amygdala	Emotional processing, fear conditioning	Emotional dysregulation, delusions, anxiety
Olfactory bulb	Smell	Hyposmia (reduced sense of smell, a supportive feature)
Autonomic ganglia / peripheral autonomic nervous system	Heart rate, BP, GI motility, bladder function	Autonomic dysfunction — orthostatic hypotension, constipation, urinary symptoms

Neurotransmitter System	Deficit in DLB	Clinical Consequence
Dopamine (nigrostriatal)	Degeneration of substantia nigra → ↓dopamine in striatum	Parkinsonism (bradykinesia, rigidity, tremor)
Acetylcholine (basal forebrain / nucleus basalis of Meynert)	Profound cholinergic loss — even greater than in AD	Cognitive impairment, attentional fluctuations, visual hallucinations
Noradrenaline (locus coeruleus)	Neuronal loss	Fluctuations in attention/arousal, orthostatic hypotension
Serotonin (dorsal raphe)	Neuronal loss	Depression, anxiety, sleep disturbance

The disproportionately severe cholinergic deficit in DLB compared to AD is a critical teaching point. It explains (1) why visual hallucinations are so prominent (cholinergic deficit in visual cortex), (2) why attentional fluctuations occur (cholinergic modulation of cortical arousal), and (3) why acetylcholinesterase (AChE) inhibitors work better in DLB than in AD.

5. Aetiology and Pathophysiology

Gene	Protein	Mechanism
SNCA	α-Synuclein	Duplication/triplication → ↑α-synuclein production → accelerated aggregation (familial DLB)
GBA	Glucocerebrosidase	Loss-of-function → impaired lysosomal clearance of α-synuclein (strongest sporadic risk factor)
APOE ε4	Apolipoprotein E	Promotes amyloid co-pathology; may directly enhance α-synuclein aggregation
BIN1, TMEM175, TPCN1, SCARB2	Various	Identified in GWAS; roles in endosomal/lysosomal function, lipid metabolism ^[3]

Why Is DLB Different from PD If Both Have Lewy Bodies?

In PD, Lewy bodies are predominantly in the brainstem (substantia nigra) → motor symptoms dominate early. In DLB, Lewy bodies are widespread in the cortex from the outset → cognitive/psychiatric symptoms dominate early. Both diseases share the same underlying pathology (α-synuclein aggregation) but differ in the distribution and timing of pathology. Think of it as a spectrum where DLB is the "cortical-predominant" form and PD is the "brainstem-predominant" form.

6. Classification

Three prodromal DLB syndromes have been proposed ^[3]:

Prodromal Syndrome	Key Features	Clinical Importance
(1) MCI due to Lewy bodies	Impaired attention, executive dysfunction, visual processing deficits with relatively preserved memory; functionally independent (does not meet criteria for dementia) ^[3]	Earliest recognisable cognitive stage; offers window for early intervention
(2) Delirium onset	Delirium as one of the initial symptoms, independent of cognitive impairment. Delirium occurs more frequently in those later diagnosed with DLB compared to AD (25% vs 7%) ^[3]	Suspect delirium-onset DLB when: (a) provoking factors not identified, (b) prolonged or recurrent delirium, (c) subsequent progressive cognitive decline ^[3]
(3) Psychiatric onset	Late-onset depressive disorder and psychosis, visual hallucinations, systematised delusions including Capgras syndrome, apathy, anxiety ^[3]	Vital to recognise due to risk of severe antipsychotic sensitivity — associated with increased morbidity and mortality ^[3]

High Yield – Delirium-Onset DLB

When encountering individuals with delirium, the clinician should inquire about other features of DLB and use caution when managing delirium with pharmacologic therapy ^[3]. Antipsychotics (commonly used for delirium) can cause catastrophic neuroleptic sensitivity reactions in undiagnosed DLB patients — leading to acute irreversible parkinsonism, loss of consciousness, or neuroleptic malignant syndrome.

Category	Criteria
Probable DLB	Dementia + ≥ 2 core clinical features, OR dementia + 1 core feature + ≥ 1 indicative biomarker
Possible DLB	Dementia + 1 core clinical feature (no indicative biomarker), OR dementia + ≥ 1 indicative biomarker only

(Core features, indicative biomarkers, and supportive features will be expanded in the Diagnosis section — here we focus on clinical features.)

7. Clinical Features

DLB produces a mixed cortical + subcortical dementia pattern. The clinical features can be organised into core features, supportive features, and the cognitive profile.

Dementia in DLB is characterised by early impairments in attention, executive function, and visuospatial function (memory is affected late) ^[2]^[4]

Cognitive Domain	Manifestation	Pathophysiological Basis
Attention	Fluctuating, poor sustained attention, easily distractible	Cholinergic deficit (nucleus basalis of Meynert → cortex) + noradrenergic deficit (locus coeruleus) disrupting arousal/attentional circuits
Executive function	Poor planning, problem-solving, multitasking, abstract reasoning	Frontal lobe Lewy body deposition + disrupted fronto-subcortical circuits (dopamine depletion in mesocortical pathway)
Visuospatial/visuoperceptual	Difficulty with spatial orientation, getting lost in familiar places, poor clock drawing, difficulty judging distances	Posterior cortical (parieto-occipital) Lewy body deposition + cholinergic deficit in visual association cortex
Memory	Relatively preserved early on — retrieval-type deficit (can improve with cueing, cf. AD where encoding is impaired)	Hippocampal structures relatively spared early (unlike AD where hippocampal atrophy is early and severe)
Language	Generally preserved early; word-finding difficulties may emerge later	Temporal lobe involvement is less prominent than in AD

Key Contrast with AD: In AD, the earliest and most prominent deficit is episodic memory (hippocampal encoding failure — information never gets stored, so cueing doesn't help). In DLB, memory is a retrieval problem (information is stored but hard to access — cueing helps). DLB patients show much more prominent attentional and visuospatial deficits than AD patients at equivalent disease stages.

7.2 Core Clinical Features

Core clinical features (must have ≥ 2 for probable DLB) ^[2]^[4]:

Cognitive fluctuations (60–80%)

Recurrent visual hallucinations (67%)

REM sleep behaviour disorder (85%)

Parkinsonism (70–90%)

These features support the diagnosis but are not core criteria:

Supportive Feature	Description	Pathophysiological Basis
Antipsychotic sensitivity (30–50%) ^[2]^[4]	Acute irreversible parkinsonism, LOC ± neuroleptic malignant syndrome (NMS) towards antipsychotics	DLB patients have profound dopaminergic depletion; typical antipsychotics (D2 blockers) cause catastrophic worsening. Even atypicals (except quetiapine/clozapine) can cause severe reactions
Repeated falls ^[2]^[4]	Frequent, often unexplained falls	Combination of postural instability, orthostatic hypotension, attentional fluctuations, and gait impairment
Syncope / transient loss of consciousness ^[2]^[4]	Recurrent syncope without clear cardiac cause	Autonomic dysfunction (orthostatic hypotension) + cardiac denervation
Autonomic dysfunction ^[2]^[4]	Orthostatic hypotension, constipation, urinary incontinence/retention, erectile dysfunction, sialorrhoea	α-Synuclein deposition in autonomic ganglia and brainstem autonomic centres → disruption of sympathetic/parasympathetic regulation
Hypersomnia ^[2]^[4]	Excessive daytime sleepiness	Disruption of brainstem sleep-wake regulatory centres (orexin/hypocretin, locus coeruleus)
Hyposmia ^[2]^[4]	Reduced sense of smell	Olfactory bulb Lewy body deposition — one of the earliest sites of α-synuclein pathology
Other hallucinations ^[2]^[4]	Auditory, tactile, olfactory hallucinations	Multisensory cortical dysfunction
Systematised delusions ^[2]^[4]	Paranoid, persecutory, or misidentification delusions (e.g., Capgras)	Fronto-temporal-limbic circuit dysfunction
Apathy, anxiety, depression ^[2]^[4]	Common psychiatric comorbidities	Serotonergic (raphe nuclei), noradrenergic (locus coeruleus), and dopaminergic (mesolimbic) deficits

Critical Safety Issue – Antipsychotic Sensitivity

Antipsychotic sensitivity is a life-threatening feature of DLB. Up to 50% of DLB patients will develop severe adverse reactions to antipsychotics — including acute irreversible parkinsonism, loss of consciousness, and neuroleptic malignant syndrome. NEVER give typical antipsychotics (haloperidol, chlorpromazine) to a patient with suspected DLB. If antipsychotics are absolutely necessary, only use quetiapine or clozapine at the lowest possible dose. It is vital to recognise the psychiatric-onset prodromal syndrome given the risk of severe antipsychotic sensitivity — associated with increased morbidity and mortality ^[3].

Autonomic dysfunction in DLB is more severe and earlier than in typical AD, because α-synuclein deposits in peripheral autonomic ganglia and brainstem autonomic centres:

System	Manifestation	Mechanism
Cardiovascular	Orthostatic hypotension (dizziness on standing, syncope)	Cardiac sympathetic denervation (demonstrable on MIBG myocardial scintigraphy — low uptake ^[3])
Gastrointestinal	Constipation (often severe), gastroparesis, dysphagia	Enteric nervous system α-synuclein deposition → impaired GI motility
Genitourinary	Urinary urgency, frequency, incontinence; erectile dysfunction	Sacral autonomic plexus involvement
Thermoregulatory	Temperature dysregulation, excessive sweating	Central and peripheral autonomic failure
Secretory	Sialorrhoea (drooling), seborrhoea	Parasympathetic dysfunction + inability to swallow saliva (dysphagia)

Feature	Symptoms (What the Patient/Carer Reports)	Signs (What You Find on Examination)
Cognitive fluctuation	"Good days and bad days," blanking out, daytime drowsiness	Variable performance on serial testing; fluctuating attention on bedside cognitive assessment
Visual hallucinations	Seeing people/animals that aren't there	May describe content in detail; may respond to hallucinations during interview
RBD	Bed partner reports violent sleep behaviour, shouting	PSG: REM sleep without atonia
Parkinsonism	Slowness, stiffness, difficulty walking, tremor	Bradykinesia (decremental finger tapping), rigidity (lead-pipe/cogwheel), rest tremor, hypomimia, stooped gait, retropulsion on pull test
Autonomic dysfunction	Dizziness on standing, constipation, urinary problems	Postural BP drop (≥ 20 mmHg systolic / ≥ 10 mmHg diastolic within 3 minutes of standing)
Falls	Recurrent unexplained falls	Postural instability, impaired pull test
Psychiatric	Depression, anxiety, paranoia, misidentification	Flat affect, psychomotor retardation, delusional content on MSE
Sleep	Excessive daytime sleepiness, vivid dreams	Drowsiness during interview, microsleeps

Feature	DLB	AD	FTD	VaD
Early cognitive domain	Attention, executive, visuospatial	Episodic memory	Personality/behaviour (bvFTD) or language (PPA)	Variable, often executive
Memory	Late, retrieval-type (cueing helps)	Early, encoding-type (cueing doesn't help)	Late	Variable
Hallucinations	Early, well-formed VH	Late if present	Uncommon	Uncommon
Motor features	Parkinsonism (bilateral, symmetric)	Usually absent early	May have MND overlap	Gait apraxia, pseudobulbar palsy
Fluctuations	Prominent	Absent	Absent	Stepwise decline
RBD	Present (85%)	Absent	Absent	Absent
Antipsychotic sensitivity	Present (30–50%)	Absent	Absent	Absent
MRI pattern	Preserved medial temporal lobe	Hippocampal/medial temporal atrophy	Frontal/temporal atrophy	White matter lesions, lacunar infarcts
SPECT/PET	Generalised ↓perfusion, most marked in occipital areas ^[2]	Bilateral posterior temporal + parietal hypoperfusion	Bilateral frontal + temporal hypoperfusion ^[5]	Correlates with infarct locations

High Yield Exam Point – MRI in DLB vs AD

DLB: preserved medial temporal lobe structures (cf AD where hippocampal atrophy is early and prominent) ^[2]. On perfusion imaging (SPECT/PET): generalised ↓perfusion and ↓metabolism, most marked in occipital areas ^[2]^[5] — the occipital hypoperfusion is relatively specific for DLB and contrasts with the posterior temporal-parietal pattern of AD.

8. Clinical Approach to a Patient with Suspected DLB

Cognitive assessment: MMSE, MoCA (MoCA is more sensitive for executive/visuospatial deficits seen in DLB)
Neurological exam: Full extrapyramidal assessment (tone, bradykinesia, tremor, gait, pull test)
Lying and standing BP (orthostatic hypotension)
General appearance: Hypomimia, drooling, stooped posture
General awareness and alertness: fluctuations may be observed during the interview ^[6]

High Yield Summary

Dementia with Lewy Bodies (DLB) — Key Points for Exams

Second most common degenerative dementia after AD (4–30%) ^[2]^[4]
Pathology: Lewy bodies (phosphorylated α-synuclein) in deep cortical layers, brainstem, and peripheral autonomic system ^[2]^[4]
AD copathology in ≥ 50% of DLB cases ^[3]
Cognitive profile: early attention, executive, visuospatial deficits; memory affected LATE ^[2]^[4]
Core features (need ≥ 2 for probable DLB): (1) Cognitive fluctuations, (2) Visual hallucinations, (3) RBD, (4) Parkinsonism ^[2]^[4]
1-year rule: DLB = dementia before/within 1yr of parkinsonism; PDD = dementia > 1yr after established PD ^[1]^[2]^[3]
Antipsychotic sensitivity is life-threatening — NEVER give typical antipsychotics ^[2]^[4]
MRI: preserved medial temporal lobe (cf AD) ^[2]
SPECT/PET: occipital hypoperfusion (cf posterior temporal-parietal in AD) ^[2]^[5]
Three prodromal syndromes: MCI-Lewy, delirium-onset, psychiatric-onset ^[3]
Survival: 5–8 years from symptom onset (shorter than AD) ^[3]
Genetics: mostly sporadic; GBA mutation is strongest sporadic RF; SNCA duplication/triplication in familial cases ^[2]^[3]
Profound cholinergic deficit → good response to AChE inhibitors ^[1]^[2]

Active Recall - Dementia with Lewy Bodies (Clinical Features & Pathophysiology)

Differential Diagnosis of Dementia with Lewy Bodies

Detailed Differentials

This is the single most important differential because DLB and PDD share identical pathology (cortical Lewy bodies).

D/dx: PD-dementia — differentiation arbitrary; generally dementia occurs in well-established Parkinsonism in PDD, whereas dementia occurs with or before Parkinsonism in DLB ^[2]^[4]

Feature	DLB	PDD
Temporal sequence	Dementia before or within 1 year of motor symptoms ^[3]	Dementia > 1 year after established PD motor symptoms
Motor onset	May be simultaneous with or after cognition	Motor symptoms well-established for years before cognition declines
Motor symmetry	More bilaterally symmetric ^[2]	Typically asymmetric onset
Response to levodopa	Variable, often partial	Usually good initial motor response (prior to dementia onset)
Hallucinations	Early, often before or concurrent with dementia	Later, often medication-related initially
RBD	Core feature from onset	Common but often noted after years of PD
Underlying pathology	Identical — cortical Lewy bodies	Identical — cortical Lewy bodies

The 1-year rule remains in effect to clinically differentiate DLB from PDD: if dementia occurs before or within 1 year of motor symptoms of bradykinesia, rigidity, or resting tremor, a diagnosis of DLB is established ^[3]. If dementia develops after 1 year of the onset of motor symptoms or an established diagnosis of PD, then the diagnosis of PDD is given ^[3].

Why does this distinction matter clinically? Although the pathology is the same, the distinction has prognostic and management implications. DLB patients tend to have a more aggressive course with earlier neuropsychiatric features and greater antipsychotic sensitivity risk, while PDD patients have had years of motor management before cognitive decline begins. DLB and PDD are both synucleinopathies with two different phenotypes with a shared underlying pathology ^[3].

High Yield – DLB vs PDD

Dopamine transporter imaging is most helpful in distinguishing DLB from Alzheimer disease ^[3], but it does NOT distinguish DLB from PDD (both show reduced DAT uptake). The 1-year rule is the primary clinical differentiator between DLB and PDD.

AD is the most common misdiagnosis given to DLB patients. The key differentiators:

Feature	DLB	AD
Early cognitive domain	Attention, executive function, visuospatial ^[2]^[4]	Episodic memory (encoding failure)
Memory profile	Retrieval deficit — improves with cueing	Encoding deficit — cueing does not help
Visual hallucinations	Early, well-formed, detailed ^[2]	Late or absent (if present, usually in advanced disease)
Cognitive fluctuations	Prominent ^[2]	Usually absent (though "sundowning" may occur in AD)
RBD	Core feature (85%)	Absent
Parkinsonism	Present in 70–90% ^[2]	Usually absent in early-moderate stages
Antipsychotic sensitivity	30–50% — severe, potentially fatal ^[2]	Not a feature
MRI	Preserved medial temporal lobe ^[2]	Early hippocampal / medial temporal lobe atrophy
SPECT/PET perfusion	Generalised ↓perfusion, most marked in occipital areas ^[2]^[5]	Bilateral posterior temporal + parietal hypoperfusion ^[5]
DAT-SPECT	Reduced dopamine transporter uptake in basal ganglia ^[3]	Normal dopamine transporter uptake
EEG	Posterior slow-wave activity with periodic fluctuations in the pre-alpha and pre-theta range ^[3]	Usually normal or shows posterior dominant rhythm slowing later

Why the overlap occurs: Copathology with Alzheimer disease occurs in more than 50% of patients with DLB. Individuals with this mix of pathology experience more memory changes and faster disease progression ^[3]. So a patient with DLB + AD copathology may present with prominent memory impairment (atypical for "pure" DLB), making the differentiation extremely difficult without biomarkers.

High Yield Exam Point – DAT-SPECT

Dopamine transporter imaging is most helpful in distinguishing DLB from Alzheimer disease ^[3]. A normal DAT scan in a patient with dementia + visual hallucinations + fluctuations argues against DLB and towards AD or other diagnoses. A reduced DAT scan supports DLB (or PDD).

Dementia with Lewy bodies is more commonly confused with delirium as fluctuations and visual hallucinations are more prominent ^[7]

This is a critical differential, especially in the hospital setting. Both DLB and delirium share:

Fluctuating attention and awareness
Visual hallucinations
Altered sleep-wake cycle
Psychomotor disturbance

Feature	DLB	Delirium
Onset	Insidious, progressive over months–years	Acute onset (hours to days) ^[8]
Course	Chronic and progressive with day-to-day fluctuations	Acute and fluctuating, with diurnal variation (worse at night) ^[8]
Identifiable precipitant	No acute systemic cause	Usually identifiable: infection, drugs, metabolic, surgery ^[8]
Duration	Years	Days to weeks (< 6 months in ICD-10)
Consciousness	Generally preserved (though may have episodes of drowsiness)	Impaired consciousness is a hallmark ^[8]
Reversibility	Not reversible	Potentially reversible when cause treated
RBD	Present	Not a feature
Parkinsonism	Spontaneous	May be drug-induced (antipsychotics used to treat delirium)

Fluctuations can occur in non-DLB delirium; therefore, fluctuations are not specific to DLB ^[3]. Visual hallucinations can also occur in non-DLB delirium and can be drug-induced or related to substance withdrawal ^[3].

Key clinical pearls:

Dementia with Lewy bodies patients are extremely vulnerable to delirium — delirium occurs more frequently in those later diagnosed with DLB compared to AD (25% vs 7%) ^[3]
Delirium should be ruled out if there is any change in pattern of fluctuation from baseline ^[4]
Suspect delirium-onset DLB when: provoking factors not identified, prolonged or recurrent delirium, subsequent progressive cognitive decline ^[3]

Fluctuations — delirium, dementia with Lewy bodies ^[6]. Both conditions should be considered when fluctuating awareness and alertness are observed.

Common Exam Trap – Delirium vs DLB

Acute onset and fluctuating course is the hallmark of delirium, distinguishing it from the gradual progressive course of dementia ^[8]^[9]. However, DLB is the dementia subtype most likely to mimic delirium because of its prominent fluctuations and VH. The key differentiator is: does the patient have an identifiable acute precipitant, and was the onset truly acute? Always search for systemic causes before attributing fluctuations to DLB.

Feature	DLB	FTD (behavioural variant)
Age at onset	~75 years	Typically younger (45–65 years)
Early features	Attention, visuospatial, executive deficits	Personality change, disinhibition, apathy, loss of empathy
Hallucinations	Early, prominent VH	Uncommon
Parkinsonism	Core feature	May occur (FTD-parkinsonism linked to MAPT/GRN mutations, or FTD-ALS)
Memory	Relatively preserved early (retrieval deficit)	Relatively preserved early
MRI	Preserved medial temporal lobes; diffuse cortical atrophy	Frontal and/or temporal atrophy (often asymmetric)
SPECT/PET	Occipital hypoperfusion	Bilateral frontal + temporal hypoperfusion ^[5]
RBD	Core feature	Not a feature
Language	Relatively preserved	May be dominant (primary progressive aphasia variants)

Why the confusion may arise: Both FTD and DLB can present with executive dysfunction, behavioural change, and apathy. However, the presence of RBD, visual hallucinations, cognitive fluctuations, and parkinsonism strongly favours DLB. Conversely, prominent disinhibition, loss of social conduct, hyperorality, and stereotyped behaviour favour bvFTD.

Feature	DLB	VaD
Onset/course	Insidious, progressive with fluctuations	Stepwise deterioration (or insidious if subcortical small vessel disease)
Vascular risk factors	Not required	Hypertension, diabetes, smoking, AF, previous stroke
Focal neurological signs	Parkinsonism (diffuse, symmetric)	Focal deficits corresponding to infarct territories
Cognitive profile	Attention, visuospatial, executive	Executive dysfunction, processing speed (subcortical pattern); variable if cortical infarcts
Hallucinations	Early, well-formed	Uncommon
RBD	Present	Absent
Neuroimaging	Preserved medial temporal lobes; no significant vascular burden	Significant white matter hyperintensities, lacunar infarcts, or strategic infarcts

Early and prominent movement disorder suggestive of dementia with Lewy bodies or other α-synucleinopathy or other nonvascular movement disorder is a feature that may suggest an alternative predominant aetiology to vascular disease ^[10].

Practical note: Cerebrovascular copathology is common in DLB (as in most elderly dementias). The question is whether the vascular burden is sufficient to explain the cognitive syndrome, or whether it is incidental. If core DLB features are present, they should not be attributed to VaD even in the presence of vascular lesions.

D/dx: NPH — no psychiatric symptoms, sleep disorder, or dysautonomic features ^[2]^[4]

Feature	DLB	NPH
Classic triad	Not present	Gait apraxia ("magnetic gait") + urinary incontinence + dementia (Hakim's triad)
Gait	Parkinsonian (stooped, shuffling, small-stepped)	Magnetic gait (feet "stuck to the floor"), wide-based
Cognitive profile	Attention, executive, visuospatial	Predominantly subcortical: psychomotor slowing, executive dysfunction
Visual hallucinations	Early, prominent	Absent
RBD	Present	Absent
Autonomic dysfunction	Present	Not a feature
Neuroimaging	Cortical atrophy (diffuse); preserved medial temporal lobes	Ventriculomegaly out of proportion to cortical atrophy
CSF dynamics	Normal	Elevated resistance to CSF outflow; improvement with large-volume LP
Reversibility	Not reversible	Potentially reversible with VP shunting

Why this matters: NPH is one of the few treatable/reversible causes of dementia. Missing NPH in favour of a DLB diagnosis means missing a potentially curable condition. Conversely, misdiagnosing DLB as NPH (because both have gait disturbance and cognitive decline) could lead to unnecessary VP shunting. The absence of psychiatric symptoms, sleep disorder, and dysautonomic features in NPH helps distinguish the two ^[2]^[4].

Red flags of atypical Parkinsonism include: early falls / postural instability, early dementia, bilateral symmetrical onset, early ANS dysfunction, poor response to L-DOPA ^[1]. Several of these overlap with DLB, making differentiation challenging:

Parkinson-Plus Syndrome	Distinguishing Features (from DLB)
Multiple System Atrophy (MSA)	Prominent dysautonomia, cerebellar signs (gait/limb ataxia, nystagmus), pyramidal signs; hot cross bun sign on MRI ^[1]. Typically NO early dementia (cognitive decline is late in MSA)
Progressive Supranuclear Palsy (PSP)	Vertical gaze palsy (especially downward), axial rigidity > appendicular, tendency to fall backwards, pseudobulbar palsy, frontal cognitive impairment; hummingbird sign / Mickey mouse sign on MRI ^[1]. No visual hallucinations, no RBD
Corticobasal Degeneration (CBD)	Marked asymmetry (clumsiness of one hand), limb apraxia, agnosia, alien limb phenomenon; dementia late ^[1]. No visual hallucinations, no fluctuations

Key teaching point: Both DLB and these Parkinson-plus syndromes are causes of atypical parkinsonism with poor response to levodopa. The differentiators are the specific non-motor features:

DLB = VH + fluctuations + RBD + early dementia
MSA = dysautonomia + cerebellar signs + no early dementia
PSP = vertical gaze palsy + axial rigidity + falls backward
CBD = asymmetric apraxia + alien limb

This differential is particularly relevant for psychiatric-onset DLB.

Feature	DLB (Psychiatric-Onset)	Late-Onset Schizophrenia / Psychosis	Late-Onset Depression
Hallucinations	Well-formed VH dominant	Auditory hallucinations dominant	May have psychotic features but VH uncommon
Delusions	Systematised (Capgras, persecutory)	Paranoid, persecutory, bizarre	Mood-congruent (guilt, worthlessness)
Parkinsonism	Spontaneous (not drug-induced)	May be drug-induced from antipsychotic treatment	Bradykinesia and bradyphrenia may overlap with parkinsonian features ^[6]
RBD	Present	Absent	Absent
Cognitive profile	Progressive executive/visuospatial decline	Cognition relatively preserved (unless chronic illness effect)	Pseudodementia — reversible with depression treatment
Antipsychotic response	Dangerous — severe sensitivity ^[2]	Therapeutic response	N/A
Course	Progressive neurodegenerative decline	Chronic relapsing-remitting	Episodic, potentially remitting

It is vital to recognise the psychiatric-onset prodromal DLB syndrome given the risk of severe antipsychotic sensitivity among individuals with DLB, which is associated with increased morbidity and mortality ^[3].

Feature	DLB	CJD (Sporadic)
Tempo	Progressive over years	Rapidly progressive — weeks to months
Cognitive decline	Gradual	Dramatically rapid
Myoclonus	Uncommon	Common and prominent
Visual hallucinations	Well-formed	Less common; visual disturbance more often cortical blindness
EEG	Posterior slowing	Periodic sharp-wave complexes
MRI	Cortical atrophy	Cortical ribboning on DWI; caudate/putamen hyperintensity
CSF	Normal or α-synuclein positive (seed amplification assay)	14-3-3 protein, RT-QuIC positive

When to think CJD: Any rapidly progressive dementia (weeks–months, not years) with myoclonus should raise red flags for CJD. The tempo alone usually distinguishes it from DLB.

Feature	DLB	PDD	AD	FTD	VaD	NPH	Delirium
Onset	Insidious	After PD	Insidious	Insidious	Stepwise/insidious	Insidious	Acute
Early cognition	Attention/exec/visuospatial	Similar to DLB	Memory	Behaviour/language	Exec/processing speed	Psychomotor slowing	Global ± attention
VH	Early	Later	Late/absent	Absent	Absent	Absent	May be present
Fluctuations	Prominent	Present	Absent	Absent	Absent	Absent	Present
RBD	Yes	Yes	No	No	No	No	No
Parkinsonism	Yes (symmetric)	Yes (asymmetric initially)	No (early)	±	± focal signs	Gait apraxia	± drug-induced
Reversible?	No	No	No	No	No	Yes (VP shunt)	Yes (treat cause)
MRI clue	Preserved MTL	Preserved MTL	MTL atrophy	Frontal/temporal atrophy	WM lesions/infarcts	Ventriculomegaly	Usually normal

High Yield Summary – Differential Diagnosis of DLB

PDD vs DLB: Use the 1-year rule — dementia before/within 1yr of parkinsonism = DLB; dementia > 1yr after PD = PDD. DAT-SPECT cannot differentiate the two ^[3].
AD vs DLB: DLB = attention/executive/visuospatial early, memory late, VH early, RBD, parkinsonism, preserved medial temporal lobes, occipital hypoperfusion. AD = memory early (encoding), no VH/RBD/parkinsonism early, hippocampal atrophy. DAT-SPECT is most helpful for distinguishing DLB from AD ^[3].
Delirium vs DLB: Acute onset + identifiable precipitant = delirium. DLB fluctuations are chronic and without acute systemic cause. DLB patients are prone to delirium (25% vs 7% AD) — always rule out superimposed delirium ^[3].
NPH: Triad of gait apraxia + incontinence + dementia; no psychiatric symptoms, sleep disorder, or dysautonomic features; potentially reversible with VP shunt ^[2]^[4].
Parkinson-plus: MSA (dysautonomia + cerebellar), PSP (vertical gaze palsy + axial rigidity), CBD (asymmetric apraxia + alien limb) — all lack the VH/RBD/fluctuation triad of DLB ^[1].
Psychiatric-onset DLB: May mimic late-onset psychosis or depression — always screen for core DLB features before prescribing antipsychotics ^[3].
Two of every three DLB cases are missed or misdiagnosed ^[3] — maintain high clinical suspicion.

Active Recall - Differential Diagnosis of DLB

References

^[1] Senior notes: Maksim Medicine Notes.pdf (Parkinson-plus syndromes, p.251) ^[2] Senior notes: Ryan Ho Neurology.pdf (Section 5.4.5 Dementia with Lewy Bodies, p.134) ^[3] Lecture slides: GC 241. Reference (3) - Patel dementia with lewy bodies.pdf ^[4] Senior notes: Ryan Ho Psychiatry.pdf (Section 4.2.5 Dementia with Lewy Bodies, p.95; Delirium DDx, p.75) ^[5] Senior notes: Ryan Ho Diagnostic Radiology.pdf (Section 8a - Cerebral Perfusion Study, p.69) ^[6] Lecture slides: Seminar 4 - Assessment for Psychogeriatrics - Dr CPW Cheng.pdf ^[7] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (Delirium DDx, p.1132) ^[8] Senior notes: Ryan Ho Fundamentals.pdf (Delirium, p.325) ^[9] AOS material: AOS - Geriatrics.pdf (Delirium vs Dementia, p.3-4) ^[10] Lecture slides: GC 241. Reference (2) - New vascular neurocognitive disorder criteria JAMA.pdf ^[11] Senior notes: learning_points_output.txt (Neurology - Two Cases of Movement Disorders)

Diagnostic Criteria, Algorithm, and Investigations for Dementia with Lewy Bodies

1. Diagnostic Criteria — 2017 Revised McKeith Criteria (Fourth Consensus Report)

The diagnosis of DLB is fundamentally clinical, supported by biomarkers. There is no single "gold standard" blood test or scan that confirms DLB in isolation — the diagnosis rests on the pattern of clinical features plus supportive investigations. The definitive diagnosis remains neuropathological (Lewy bodies on post-mortem), but in clinical practice the 2017 McKeith criteria are used.

Core clinical features ^[3]^[4]:

#	Core Feature	Description
1	Fluctuating cognition	Pronounced variations in attention and alertness
2	Recurrent visual hallucinations	Well-formed and detailed, often of people, children, and animals. Passage hallucinations, sense of presence, and visual illusions may also occur concurrently. Insight may vary
3	REM sleep behaviour disorder	May precede other symptoms
4	One or more spontaneous features of parkinsonism	Bradykinesia, rest tremor, or rigidity

Indicative biomarkers ^[3]:

Biomarker	What It Shows	Why It Helps
Reduced dopamine transporter uptake in basal ganglia by SPECT or PET	Nigrostriatal dopaminergic degeneration	Most helpful in distinguishing DLB from Alzheimer disease ^[3] — normal DAT in AD, reduced in DLB
Abnormal (low uptake) iodine-123 MIBG myocardial scintigraphy	Postganglionic cardiac sympathetic denervation	Demonstrates peripheral autonomic involvement specific to α-synucleinopathies; not available everywhere
REM sleep without atonia confirmed on polysomnography	Objective confirmation of RBD (loss of normal REM muscle atonia)	Converts a clinical history of "dream enactment" into a confirmed biomarker

Supportive biomarkers ^[3]:

Biomarker	Expected Finding in DLB
CT and MRI	Relative preservation of medial temporal lobe structures (cf. AD where hippocampal atrophy occurs early)
SPECT and PET	Generalized low uptake with reduced occipital activity; posterior cingulate island sign on FDG-PET
EEG	Posterior slow-wave activity with periodic fluctuations in the pre-alpha and pre-theta range

Probable DLB ^[3]:

Two or more core clinical features, OR one core clinical feature plus one or more indicative biomarkers

Possible DLB ^[3]:

One core clinical feature only (no indicative biomarker), OR one or more indicative biomarkers only (no core clinical features)

Category	Criteria
Probable DLB	≥ 2 core features, OR 1 core feature + ≥ 1 indicative biomarker
Possible DLB	1 core feature alone (no indicative biomarker), OR ≥ 1 indicative biomarker alone (no core features)

Logic of the system: The classification is designed to be hierarchical. Core clinical features carry the most diagnostic weight because they are the clinical hallmarks of Lewy body pathology. Indicative biomarkers can "substitute" for a missing core feature because they provide objective evidence of the underlying pathology (dopaminergic degeneration, autonomic denervation, or REM sleep dysregulation). Supportive biomarkers and supportive clinical features increase confidence but cannot substitute for core features.

High Yield – Probable vs Possible DLB

For probable DLB, you need either two core features or one core feature plus one indicative biomarker. A common exam scenario: a patient with dementia + fluctuations (1 core) + reduced DAT uptake on SPECT (1 indicative biomarker) = probable DLB. A patient with dementia + visual hallucinations only (1 core, no biomarker) = possible DLB.

Research criteria for MCI due to Lewy bodies ^[3]:

Component	Criteria
Required features	Concern by patient, care partner, or clinician for cognitive decline; impairment in one or more cognitive domains (most commonly attention, executive function, and visual processing); independent in functional activities, does not meet criteria for dementia
Core clinical features	Same 4 as DLB: fluctuations, VH, RBD, parkinsonism
Proposed biomarkers	Reduced DAT uptake, PSG-confirmed RSWA, abnormal MIBG
Probable MCI-LB	≥ 2 core features, or 1 core feature + ≥ 1 biomarker
Possible MCI-LB	1 core feature alone, or ≥ 1 biomarker alone

3. Investigations — Modalities, Key Findings, and Interpretation

The investigations in DLB serve three purposes: (1) support the diagnosis, (2) distinguish DLB from mimics (especially AD), and (3) exclude reversible causes of dementia.

Tool	What It Tests	DLB-Specific Points
MoCA (Montreal Cognitive Assessment)	Executive function, attention, visuospatial, memory, language, orientation	Preferred over MMSE because it is more sensitive for executive and visuospatial deficits ^[3] — the very domains impaired early in DLB. MMSE is biased towards memory/orientation and may underestimate DLB severity
MMSE	Orientation, registration, recall, attention, language, visuospatial	Less sensitive for DLB; may be relatively preserved in early DLB because memory/orientation are spared initially
Clock Drawing Test	Visuospatial and executive function	Often strikingly impaired in DLB — patients produce disorganised clock faces with spatial errors, out of proportion to their MMSE score

Neuropsychological testing should be pursued ^[3] with a battery assessing:

Executive function and attention: trail-making tests, Stroop task, phonemic fluency test, Wisconsin Card Sorting Test ^[3]
Visuospatial: figure copy tasks (intersecting pentagons, complex figures), line orientation, size matching, fragmented letters test, and the pareidolia test ^[3]

The pareidolia test is a tool that evokes and measures visual hallucination-like illusions of meaningful objects from ambiguous visual scenes ^[3]. This is uniquely useful in DLB because patients with posterior cortical dysfunction "see" meaningful images in random patterns at much higher rates than AD or healthy controls.

Why MoCA Over MMSE in DLB?

The MMSE allocates 10/30 points to orientation and 3/30 to recall — both relatively preserved early in DLB. It has only 1 point for visuospatial (pentagon copy) and minimal executive testing. The MoCA includes trail-making (executive), cube copy and clock drawing (visuospatial), digit span and serial 7s (attention), and verbal fluency (executive) — precisely the domains affected in DLB. A patient with early DLB might score 24/30 on MMSE ("normal") but 18/30 on MoCA (clearly impaired).

3.3 Structural Neuroimaging

In patients with DLB, there may be generalised cortical atrophy in a nonspecific pattern with preservation of the medial temporal lobes ^[3]

Sequence	Finding in DLB	Clinical Interpretation
T1-weighted (volumetric)	Relative preservation of medial temporal lobe structures ^[2]^[4] — including hippocampus	Key differentiator from AD, where hippocampal atrophy occurs early. In DLB, hippocampal volume is relatively normal because pathology targets cortex diffusely rather than hippocampus selectively
T1-weighted	Generalised cortical atrophy (non-specific)	Present in most neurodegenerative dementias; not diagnostic
T2/FLAIR	Assess for white matter hyperintensities (WMH)	Helps quantify vascular burden. Extensive WMH may suggest coexisting VaD or mixed dementia
DWI	No restricted diffusion (unlike CJD)	Helps exclude CJD (which shows cortical ribboning and basal ganglia restricted diffusion)
SWI/GRE	Assess for microbleeds	Extensive microbleeds may suggest cerebral amyloid angiopathy (can co-occur with DLB)

It is important to note that medial temporal atrophy, particularly of the hippocampus, is suggestive of Alzheimer disease; however, co-occurring dementia due to both Alzheimer disease and DLB should still be considered based on other clinical and biomarker findings ^[3]. This is critical — the presence of hippocampal atrophy does not exclude DLB; it may simply indicate AD copathology (present in > 50% of DLB cases).

3.4 Functional Neuroimaging

This is the single most important investigation for supporting a DLB diagnosis in clinical practice.

Radiopharmaceutical: ¹²³I-FP-CIT (DaTscan) for SPECT, or ¹⁸F-DOPA / ¹⁸F-FE-PE2I for PET
What it measures: Presynaptic dopamine transporter (DAT) density in the striatum (caudate and putamen). DAT is a protein on presynaptic dopaminergic nerve terminals that reuptakes dopamine from the synapse.
Normal: Symmetric, comma-shaped uptake in bilateral caudate and putamen ("comma" or "tadpole" shape)
DLB finding: Reduced dopamine transporter uptake in basal ganglia ^[3] — loss of the "tail" (putaminal uptake reduced first, then caudate), creating a "full stop" or "period" shape instead of a "comma"

DAT-SPECT Result	Interpretation
Normal	Argues against DLB (and PD/PDD); consider AD, FTD, VaD, psychiatric
Reduced uptake bilaterally	Supports DLB (or PDD/PD); does NOT distinguish DLB from PDD
Asymmetrically reduced	May suggest PD/PDD (typically more asymmetric) rather than DLB (more symmetric), though overlap exists

Dopamine transporter imaging is most helpful in distinguishing DLB from Alzheimer disease ^[3]

Why?: In AD, nigrostriatal neurons are intact → DAT is normal. In DLB, nigrostriatal degeneration → reduced DAT. This is a fundamental pathological difference: AD is primarily a tauopathy/amyloidopathy affecting hippocampus and association cortex, while DLB is an α-synucleinopathy affecting nigrostriatal and cortical neurons. The DAT scan detects this nigrostriatal component.

Limitations: Cannot distinguish DLB from PDD (both have nigrostriatal degeneration). Cannot distinguish DLB from other causes of nigrostriatal loss (MSA, PSP, CBD). Drug-induced parkinsonism has a normal DAT scan.

High Yield – DAT-SPECT Interpretation

Reduced DAT uptake = indicative biomarker for DLB. Combined with 1 core clinical feature, it establishes probable DLB. A normal DAT scan in a patient with dementia and visual hallucinations should make you reconsider the DLB diagnosis (though it doesn't exclude it completely — sensitivity ~78%).

Cerebral perfusion study: demonstrates perfusion to specific brain areas; different types of dementia typically present with different patterns of perfusion changes ^[5]

Dementia Type	SPECT/PET Pattern
DLB	Generalised ↓perfusion and ↓metabolism, most marked in occipital areas ^[2]; posterior cingulate island sign on FDG-PET ^[3]
AD	Bilateral posterior temporal + parietal hypoperfusion ^[5]
FTD	Bilateral frontal + temporal hypoperfusion ^[5]
VaD	Patchy, asymmetric deficits correlating with infarct territories

Key DLB-specific patterns explained:

Occipital hypoperfusion/hypometabolism: The occipital lobes (primary and association visual cortex) are preferentially affected in DLB, correlating with the prominent visual hallucinations and visuospatial deficits. This pattern is relatively specific for DLB and is NOT seen in early AD.
Posterior cingulate island sign: On FDG-PET, AD characteristically shows decreased metabolism in the posterior cingulate cortex (one of the earliest and most affected regions in AD). In DLB, the posterior cingulate is relatively spared (creating an "island" of preserved metabolism against a background of generalised and occipital hypometabolism). This relative preservation creates a useful visual discriminator between DLB and AD on FDG-PET.

Radiopharmaceutical for SPECT: 99mTc-HMPAO ^[5] (hexamethylpropyleneamine oxime) — a lipophilic tracer that crosses the blood-brain barrier and distributes proportionally to regional cerebral blood flow.

EEG: posterior slow-wave activity with periodic fluctuations in the pre-alpha and pre-theta range ^[3]

Finding	Clinical Significance
Posterior dominant rhythm slowing (< 8 Hz)	Observed in ~90% of DLB patients vs ~10% of AD patients ^[3] — highly discriminative
Periodic fluctuations	Correlates with clinical cognitive fluctuations
Generalised slowing	Non-specific but worse than expected for dementia severity

Why it helps: The combination of posterior slowing plus periodic fluctuations has good sensitivity for DLB and helps differentiate from AD (where EEG is usually normal or shows less specific changes early on). EEG also excludes non-convulsive status epilepticus (NCSE) — a critical differential that requires EEG for detection.

3.7 Synuclein-Specific Markers (Emerging Biomarkers)

Given that AD copathology is observed in at least 50% of individuals with DLB ^[3], assessing for coexisting AD pathology is clinically relevant:

Biomarker	What It Shows
CSF Aβ42/Aβ40 ratio	Low ratio suggests brain amyloid deposition (AD copathology)
CSF phospho-tau (p-tau 181, p-tau 217)	Elevated in AD; helps determine extent of tau copathology
Amyloid PET (¹⁸F-florbetapir, flutemetamol, florbetaben)	Visualises brain amyloid plaques directly; positive in ~50% of DLB patients (reflecting copathology)
Plasma p-tau 217	Emerging blood-based biomarker for AD pathology; useful for screening

Clinical significance: Positive AD biomarkers in a DLB patient indicate mixed pathology. These patients tend to have greater cognitive decline, greater risk of institutionalisation, and mortality ^[3]. This also explains why some DLB patients present with prominent memory impairment — the amnestic component is driven by the coexisting AD pathology.

Every dementia workup must include screening for reversible causes (which account for 10–15% of dementia presentations) ^[2]:

Investigation	What It Excludes
CBC	Anaemia, B12/folate deficiency (macrocytic anaemia), infection
RFT (renal function)	Uraemic encephalopathy
LFT	Hepatic encephalopathy
TFT (thyroid function)	Hypothyroidism (reversible cause of cognitive decline)
Calcium	Hypercalcaemia (confusion, cognitive impairment)
Glucose	Hypoglycaemia, uncontrolled diabetes
Vitamin B12 and folate	B12 deficiency causes reversible dementia
Syphilis serology (VDRL/RPR)	Neurosyphilis (rare but treatable)
HIV (if risk factors)	HIV-associated neurocognitive disorder
ESR/CRP	Screen for inflammatory/infective causes

Category	Investigation	Expected Finding in DLB	Role
Bedside	MoCA	Impaired attention, executive, visuospatial; memory relatively spared	Screening; profile characterisation
Indicative biomarker	DAT-SPECT/PET	Reduced striatal uptake	Distinguishes DLB from AD
Indicative biomarker	MIBG scintigraphy	Low cardiac uptake	Cardiac sympathetic denervation
Indicative biomarker	PSG	RSWA confirmed	Confirms RBD objectively
Supportive biomarker	MRI brain	Preserved medial temporal lobes; generalised atrophy	Excludes AD atrophy pattern, VaD, NPH, structural
Supportive biomarker	FDG-PET / perfusion SPECT	Occipital hypometabolism; posterior cingulate island sign	Pattern recognition for DLB vs AD vs FTD
Supportive biomarker	EEG	Posterior slowing < 8 Hz; periodic fluctuations	Distinguishes from AD; excludes NCSE
Emerging	CSF α-synuclein SAA	Positive seeding	Confirms α-synucleinopathy (not DLB-specific)
Emerging	Skin biopsy for phospho-α-synuclein	Positive in cutaneous nerve fibres	Confirms α-synucleinopathy (not DLB-specific)
Copathology	CSF Aβ42/40, p-tau; Amyloid PET	May be positive in > 50%	Detects AD copathology
Routine	Bloods (CBC, RFT, LFT, TFT, B12, folate, Ca, glucose, syphilis)	Normal (or reveals reversible cause)	Excludes treatable mimics

Consider a typical exam scenario:

An 76-year-old man presents with 18 months of progressive cognitive decline, well-formed visual hallucinations of children in his living room, episodes of staring blankly ("blanking out"), and mild bilateral rigidity with bradykinesia. His wife reports he shouts and thrashes in his sleep. MMSE 22/30, MoCA 15/30.

Step-by-step reasoning:

Dementia? Yes — progressive cognitive decline impairing function (retired from work, wife manages finances)
Cognitive profile? MoCA 15 (worse than MMSE 22) → attention/executive/visuospatial disproportionately affected → DLB pattern
Core features? VH (well-formed ✓), fluctuations ("blanking out" ✓), RBD (shouting/thrashing in sleep ✓), parkinsonism (bilateral rigidity + bradykinesia ✓) → 4 core features
Diagnosis: ≥ 2 core features → Probable DLB (no biomarker even needed)
Timing: Cognitive decline started 18 months ago; parkinsonism also present → dementia concurrent with/before parkinsonism → consistent with DLB (not PDD)
Investigations: MRI (preserved MTL, exclude other causes), bloods (exclude reversible causes), consider DAT-SPECT if any diagnostic uncertainty

High Yield Summary — Diagnostic Criteria and Investigations for DLB

2017 McKeith Criteria: Required = progressive cognitive decline with functional impairment. 4 core features: fluctuations, VH, RBD, parkinsonism. ≥ 2 core features = probable DLB; 1 core + 1 indicative biomarker = probable DLB ^[3].
Three indicative biomarkers: reduced DAT uptake (SPECT/PET), low MIBG cardiac uptake, PSG-confirmed RSWA ^[3].
Three supportive biomarkers: preserved MTL on MRI, occipital hypometabolism on FDG-PET/SPECT (with posterior cingulate island sign), posterior EEG slowing ^[3].
DAT-SPECT is most helpful for distinguishing DLB from AD ^[3] — normal DAT argues against DLB.
MoCA preferred over MMSE because it tests executive and visuospatial domains more thoroughly ^[3].
α-Synuclein SAA (CSF) and skin biopsy confirm α-synucleinopathy but are NOT specific for DLB vs PD/PDD ^[3].
AD copathology in > 50% of DLB — consider AD biomarkers (CSF Aβ/p-tau, amyloid PET) ^[3].
EEG: posterior slowing < 8 Hz in ~90% DLB vs ~10% AD — highly discriminative ^[3].
Always screen for reversible causes of dementia: TFT, B12, folate, syphilis, calcium, glucose ^[2].

Active Recall - DLB Diagnostic Criteria and Investigations

References

^[2] Senior notes: Ryan Ho Neurology.pdf (Section 5.4 Dementia and Dementia Syndromes, p.128; Section 5.4.5 DLB, p.134) ^[3] Lecture slides: GC 241. Reference (3) - Patel dementia with lewy bodies.pdf ^[4] Senior notes: Ryan Ho Psychiatry.pdf (Section 4.2.5 Dementia with Lewy Bodies, p.95) ^[5] Senior notes: Ryan Ho Diagnostic Radiology.pdf (Section 8a - Cerebral Perfusion Study, p.69) ^[12] Senior notes: Maksim Medicine Notes.pdf (DLB section, p.253)

Management of Dementia with Lewy Bodies

Detailed Treatment Modalities

This is the first and most important step in DLB management. Many commonly prescribed medications can dramatically worsen DLB symptoms.

A comprehensive medication review should be conducted at each evaluation to ensure the person with LBD is not taking medications or over-the-counter drugs that may worsen their cognition or trigger psychosis ^[3]

Drug Class	Examples	Why It Is Harmful in DLB	Action
Typical antipsychotics	Haloperidol, chlorpromazine	Antipsychotic sensitivity (30–50%): acute irreversible parkinsonism, LOC ± NMS ^[2]^[4]	Absolutely contraindicated
Most atypical antipsychotics	Risperidone, olanzapine, aripiprazole	Still carry significant risk of neuroleptic sensitivity in DLB (less than typicals but still dangerous)	Avoid — only quetiapine or clozapine if essential
Anticholinergic medications	Oxybutynin, trihexyphenidyl, tricyclic antidepressants, diphenhydramine	Worsen cognitive impairment by further depleting already critically low cholinergic transmission; can precipitate delirium and hallucinations	Stop and replace
OTC anticholinergic sleep aids	Diphenhydramine ^[3]	Same mechanism — anticholinergic, worsens cognition	Stop
Dopamine agonists	Pramipexole, ropinirole, rotigotine	More likely to cause hallucinations and impulse control disorders than levodopa	Avoid (use levodopa instead if motor treatment needed)
Benzodiazepines (chronic)	Diazepam, temazepam	Worsen cognition, increase fall risk, can cause paradoxical agitation	Taper and stop unless used for RBD (clonazepam)
Antihistamines	Promethazine, cyclizine	Anticholinergic properties	Avoid

Avoid the use or minimise the use of antipsychotics and anticholinergic medications in individuals suspected of having delirium-onset DLB ^[3]. Avoid the use or minimise the use of antipsychotics and anticholinergic medications in individuals suspected of having psychiatric-onset DLB ^[3].

High Yield – Drugs to AVOID in DLB

Must never give: Typical antipsychotics (haloperidol, chlorpromazine) — risk of catastrophic irreversible parkinsonism, NMS, and death. Should avoid: Most atypical antipsychotics (except quetiapine/clozapine at lowest dose), all anticholinergics (including OTC diphenhydramine), dopamine agonists. This is one of the most commonly examined safety points in DLB.

2. Non-Pharmacological Interventions

Non-pharmacological approaches are the foundation of DLB management and should be initiated before or alongside pharmacotherapy for every symptom domain.

Intervention	Rationale	Details
Cognitive stimulation therapy	Maintains residual cognitive function; engages preserved pathways	Structured group activities, reminiscence therapy, reality orientation
Structured daily routines	Reduces disorientation and anxiety; compensates for executive dysfunction	Consistent schedule for meals, activities, sleep; visual timetables
Environmental modification	Reduces confusion, misperception, and falls	Good lighting (reduces VH which worsen in low light); declutter; contrast markings on stairs; remove mirrors (can trigger misidentification)
Caregiver education	Critical for safety and quality of life	Explain fluctuations ("good days/bad days are part of the disease"), VH management (reassure, don't argue), fall prevention, driving safety

Measure	Why
Remove sharp/hard objects from bedside	Prevent injury during dream enactment
Place mattress on floor or use bed rails with padding	Prevent falling out of bed
Bed partner may need to sleep separately	Protect bed partner from injury
Secure bedroom environment	Lock windows, remove weapons/objects that could be grabbed during RBD episode

3. Pharmacological Treatment — By Symptom Domain

3.1 Cognition and Neuropsychiatric Symptoms

Cholinesterase inhibitor: often 1st line due to C/I to antipsychotics ^[4]

Aspect	Details
Agents	Donepezil (Aricept), galantamine (Reminyl), rivastigmine (Exelon) ^[13]
Mechanism of Action	Inhibit acetylcholinesterase (AChE) → ↓breakdown of acetylcholine (ACh) at synapses → ↑cholinergic transmission. Based on the cholinergic hypothesis: DLB has profound cholinergic deficit (even more severe than AD) due to degeneration of the nucleus basalis of Meynert
Effect on cognition	Modest but meaningful improvement in attention, executive function, global cognition
Effect on neuropsychiatric symptoms	Reduces visual hallucinations, apathy, and anxiety — this is why AChE inhibitors are first-line for both cognition AND BPSD in DLB. By restoring cholinergic tone in the visual cortex, VH frequency and severity decrease
Effect on fluctuations	May reduce the severity and frequency of cognitive fluctuations
Advantage in DLB vs AD	DLB patients often show better response to AChE inhibitors than AD patients because their cholinergic deficit is more severe (more room for improvement) and the cortical neurons receiving the cholinergic input are relatively intact (unlike AD where cortical neurons are also lost)
Dose	Start low, titrate slowly (e.g. donepezil 5 mg → 10 mg after 4–6 weeks)
Side effects	GI: nausea, vomiting, diarrhoea, anorexia (cholinergic excess in gut). Cardiovascular: bradycardia, syncope (vagotonic effect). Neurological: vivid dreams, muscle cramps
Caution	Can worsen parkinsonism (rare) — but this is much less of a concern than the benefit for cognition/hallucinations. Bradycardia risk — check ECG before starting (avoid if significant conduction abnormality)

Why AChE inhibitors work better in DLB than AD — a first-principles explanation: In DLB, the cholinergic neurons in the nucleus basalis are severely depleted, but the postsynaptic cortical neurons they project to are relatively intact. AChE inhibitors increase the amount of ACh available at the synapse, and because the postsynaptic machinery is still functional, the signal is amplified effectively. In AD, both the cholinergic neurons AND the cortical target neurons are destroyed, so there are fewer functional synapses to amplify.

High Yield – AChE Inhibitors Are First Line in DLB

Cholinesterase inhibitors are first-line treatment for BOTH cognitive symptoms AND neuropsychiatric symptoms (including visual hallucinations) in DLB ^[2]^[4]. They are preferred over antipsychotics because antipsychotics are dangerous in DLB. Always trial an AChE inhibitor before considering any antipsychotic.

Memantine: mixed evidence, minimal effect ^[4]

Aspect	Details
Mechanism	NMDA receptor antagonist → blocks excessive glutamatergic excitotoxicity which contributes to neuronal death
Evidence in DLB	Some studies suggest modest benefit for global cognition and behavioural symptoms; other studies show no significant benefit. Overall evidence is mixed
Use	May be tried as add-on therapy to AChE inhibitors in moderate-severe DLB, or as monotherapy if AChE inhibitors are not tolerated
Side effects	Dizziness, headache, constipation, confusion (relatively well-tolerated)

Atypical antipsychotics: low dose only, only when BPSD is very severe ^[4]

Aspect	Details
When to use	ONLY when behavioural/psychiatric symptoms are severe enough to pose a safety risk to the patient or others, AND non-pharmacological approaches + AChE inhibitors have failed
Safe agents	Quetiapine (lowest effective dose, e.g. 12.5–25 mg) or clozapine (requires regular blood monitoring for agranulocytosis) ^[4]^[12]
Why quetiapine?	Quetiapine has the weakest D2 receptor binding of all atypical antipsychotics → least likely to worsen parkinsonism. It has stronger 5-HT2A and H1 binding, providing sedation and antipsychotic effect with minimal extrapyramidal side effects
Why clozapine?	Also has very weak D2 binding; proven efficacy in PD-psychosis (similar pathology). However, requires regular FBC monitoring due to risk of agranulocytosis (1–2%)
Absolutely contraindicated	Typical antipsychotics (haloperidol, chlorpromazine) — risk of irreversible parkinsonism, LOC, NMS ^[2]^[4]
Avoid	Risperidone, olanzapine, aripiprazole — still carry significant neuroleptic sensitivity risk in DLB
Dose	Start at the lowest possible dose and titrate extremely slowly. Use for the shortest possible duration
Monitoring	Close observation for worsening parkinsonism, sedation, falls, metabolic effects

Only very low doses of atypical antipsychotics should be considered in DLB due to the antipsychotic sensitivity phenomenon ^[2]^[4]

Antipsychotic	D2 Binding Affinity	Safety in DLB
Haloperidol	Very strong	ABSOLUTELY CONTRAINDICATED
Risperidone	Strong	Avoid
Olanzapine	Moderate	Avoid
Aripiprazole	Moderate (partial agonist)	Avoid
Quetiapine	Weak	Safest — preferred if antipsychotic needed
Clozapine	Weak	Safe but requires FBC monitoring

REM sleep behaviour disorder: melatonin, clonazepam ^[4] ^[12]

Agent	Mechanism	Details
Melatonin (1st line)	Endogenous sleep-wake regulator; stabilises REM sleep architecture; reduces REM muscle activity through uncertain mechanisms (may modulate GABAergic tone in REM-regulatory pontine nuclei)	Dose: 3–12 mg at bedtime. Safe and well-tolerated. No sedation hangover, no falls risk, no cognitive impairment. Preferred first-line in elderly and in patients with concurrent cognitive decline
Clonazepam (2nd line)	Benzodiazepine; enhances GABA-A receptor activity → suppresses phasic muscle activity during REM sleep	Dose: 0.25–0.5 mg at bedtime (start low). Caution in DLB: can worsen daytime drowsiness, cognitive impairment, increase fall risk, and worsen sleep-disordered breathing (OSA). Generally reserved for patients who fail melatonin

Non-pharmacological measures (first and always):

Bedroom safety modifications as described above
Bed partner safety

RBD Treatment Priority

Melatonin is first-line for RBD in DLB because it is safe and does not impair cognition or increase falls. Clonazepam is effective but carries fall risk and cognitive side effects in this vulnerable population. Always combine pharmacotherapy with bedroom safety measures.

Parkinsonism: levodopa ^[2] / similar to Tx in PD ^[4] / levodopa-carbidopa ^[12]

Aspect	Details
First-line agent	Levodopa-carbidopa (co-careldopa, Sinemet, Madopar)
Why levodopa over dopamine agonists?	Levodopa is the least likely dopaminergic agent to cause psychiatric side effects (hallucinations, psychosis, impulse control disorders). Dopamine agonists (pramipexole, ropinirole) are far more likely to provoke or worsen hallucinations in DLB — they should be avoided
Mechanism	Levodopa is the metabolic precursor to dopamine. It crosses the blood-brain barrier (carbidopa does not — it inhibits peripheral DOPA decarboxylase, preventing peripheral conversion and reducing nausea/vomiting). In the brain, levodopa is converted to dopamine by DOPA decarboxylase → replenishes striatal dopamine → improves motor symptoms
Expected response	Variable and often partial (unlike the robust response seen in idiopathic PD). DLB parkinsonism is more resistant to levodopa because the postsynaptic striatal neurons are also affected (not just the presynaptic nigrostriatal input)
Dose	Start very low (e.g. Madopar 62.5 mg BD or TDS), titrate slowly over weeks
Risk	Can worsen hallucinations and psychosis — this is the treatment dilemma in DLB. If hallucinations worsen on levodopa: reduce dose, add/optimise AChE inhibitor, consider low-dose quetiapine
What to avoid	Amantadine (can worsen confusion/hallucinations), selegiline/rasagiline (less predictable, more psychiatric SE), dopamine agonists (worst for hallucinations)

The approach to DLB parkinsonism mirrors what is done in PD drug-induced psychosis: Levodopa is least likely [to cause psychosis]. Mx: ↓amantadine/selegiline → ↓DA agonist → ↓levodopa → start atypical antipsychotics (clozapine) ^[12]

Symptom	Treatment	Mechanism / Rationale
Orthostatic hypotension	Non-pharmacological first: increase fluid/salt intake, compression stockings, slow position changes, elevate head of bed. Pharmacological: fludrocortisone (mineralocorticoid → ↑Na+/H₂O retention → ↑intravascular volume), midodrine (α1-agonist → peripheral vasoconstriction → ↑standing BP)	Orthostatic hypotension in DLB is due to cardiac sympathetic denervation + loss of baroreceptor-mediated vasoconstriction
Constipation	Stool softeners, osmotic laxatives (lactulose, macrogol)	Enteric nervous system α-synuclein deposition → ↓GI motility
Urinary symptoms	Avoid traditional anticholinergics (oxybutynin, tolterodine) — they will worsen cognition. Consider mirabegron (β3-adrenergic agonist → relaxes detrusor without anticholinergic effects), or desmopressin for nocturia	Anticholinergics are contraindicated because DLB already has severe cholinergic deficit
Sialorrhoea	Glycopyrrolate (quaternary ammonium anticholinergic that does not cross BBB → reduces salivation without worsening cognition), botulinum toxin to salivary glands	Drooling is due to impaired swallowing rather than excess saliva production
Erectile dysfunction	Sildenafil (PDE-5 inhibitor) — but caution with orthostatic hypotension risk	Autonomic denervation of genital vasculature

Autonomic Symptom Trap

The biggest pitfall in managing autonomic symptoms in DLB is using anticholinergic drugs for urinary urgency (oxybutynin, solifenacin). These worsen cognition, increase confusion, and can precipitate delirium. Use mirabegron (β3-agonist, non-anticholinergic) instead.

SSRIs: for depression ^[2]^[4]

Agent	Details
SSRIs (sertraline, citalopram, escitalopram)	First-line for depression in DLB. Selective serotonin reuptake inhibitors increase serotonergic tone by blocking presynaptic serotonin transporters → ↑serotonin in synaptic cleft. Well-tolerated, no anticholinergic effects, no worsening of parkinsonism
Avoid tricyclic antidepressants (amitriptyline, nortriptyline)	Strong anticholinergic properties → worsen cognition, cause urinary retention, constipation, cardiac conduction abnormalities
SNRIs (venlafaxine, duloxetine)	Alternative if SSRIs fail; watch for hypertension and nausea
Mirtazapine	May help with insomnia and appetite loss; H1 antagonism causes sedation. Relatively safe but monitor for weight gain
Caution with SSRIs and RBD	Some antidepressants (especially SSRIs and SNRIs) can exacerbate or unmask RBD. Monitor sleep symptoms when starting

Symptom Domain	First Line	Second Line	Contraindicated
Cognition	AChE inhibitors (donepezil, rivastigmine, galantamine)	Memantine (add-on or if AChE inhibitors not tolerated)	Anticholinergics
Visual hallucinations / psychosis	AChE inhibitors	Very low-dose quetiapine or clozapine (only if severe)	Typical antipsychotics; most atypical antipsychotics
RBD	Melatonin	Clonazepam (low dose)	-
Parkinsonism	Levodopa-carbidopa	-	Dopamine agonists; anticholinergic anti-parkinsonian drugs (trihexyphenidyl)
Depression	SSRIs	SNRIs, mirtazapine	TCAs (anticholinergic)
Orthostatic hypotension	Fludrocortisone, midodrine	Droxidopa	-
Constipation	Osmotic laxatives	-	-
Urinary symptoms	Mirabegron	-	Anticholinergic bladder agents (oxybutynin)
Fluctuations	AChE inhibitors	Modafinil (for daytime somnolence)	-

DLB progresses faster than Alzheimer disease ^[3]:

Survival approximately 5–8 years from symptom onset ^[3]
Average lifespan 7.7 years ^[4]
Most common cause of death: failure to thrive (65%), pneumonia and swallowing difficulties (23%), other medical conditions (19%), complications from a fall (10%) ^[3]
Copathology with AD accelerates decline
Factors associated with worse prognosis: older age at onset, AD copathology, more severe autonomic dysfunction, early institutionalisation

High Yield Summary — Management of DLB

No disease-modifying therapy available — all treatment is symptomatic ^[2]^[3]^[4]
Step 1: Comprehensive medication review — stop anticholinergics, antihistamines, OTC sleep aids (diphenhydramine), typical antipsychotics ^[3]
Step 2: Non-pharmacological interventions — cognitive stimulation, bedroom safety for RBD, fall prevention, caregiver education, advance care planning
Cognition + VH: AChE inhibitors are first-line (donepezil, rivastigmine, galantamine) — work better in DLB than AD due to more severe cholinergic deficit ^[2]^[4]
Psychosis (severe BPSD only): very low-dose quetiapine or clozapine only — NEVER typical antipsychotics ^[2]^[4]^[12]
RBD: melatonin first-line, clonazepam second-line ^[4]^[12]
Parkinsonism: levodopa-carbidopa — avoid dopamine agonists (worsen hallucinations) ^[2]^[4]^[12]
Depression: SSRIs — avoid TCAs (anticholinergic) ^[2]^[4]
Autonomic: avoid anticholinergic bladder drugs — use mirabegron for urinary symptoms, fludrocortisone/midodrine for orthostatic hypotension
Prognosis: 5–8 years survival; faster progression than AD ^[3]^[4]
Advance care planning is essential — discuss early with patient and family ^[3]

Active Recall - Management of DLB

References

^[2] Senior notes: Ryan Ho Neurology.pdf (Section 5.4.5 DLB Treatment, p.134) ^[3] Lecture slides: GC 241. Reference (3) - Patel dementia with lewy bodies.pdf ^[4] Senior notes: Ryan Ho Psychiatry.pdf (Section 4.2.5 DLB Treatment, p.95) ^[12] Senior notes: Maksim Medicine Notes.pdf (DLB Treatment, p.253; PD drug-induced psychosis, p.252) ^[13] Senior notes: Ryan Ho Psychiatry.pdf (AD Pharmacological Management, p.92)

Complications of Dementia with Lewy Bodies

DLB is a relentless, progressive neurodegenerative disease. Its complications arise from the interplay of cognitive decline, neuropsychiatric disturbance, motor impairment, autonomic failure, and the iatrogenic hazards that are uniquely dangerous in this population. Understanding complications from first principles — linking each back to the underlying α-synuclein-driven neurodegeneration — is essential for both exams and clinical practice.

Mechanism	Explanation
Parkinsonism	Bradykinesia, rigidity, postural instability → impaired righting reflexes, shuffling gait, festination
Orthostatic hypotension	Autonomic denervation → failure of baroreceptor-mediated vasoconstriction on standing → cerebral hypoperfusion → presyncope / syncope → fall
Cognitive fluctuations	Episodes of "blanking out" or impaired attention → patient is unaware of environmental hazards during "off" periods
Visual hallucinations / visuospatial deficits	Misperception of environment (depth, spatial orientation) → misjudgement of stairs, curbs, obstacles
Medications	Sedatives (clonazepam for RBD), antihypertensives (worsening orthostatic hypotension), levodopa (initial hypotension)

Complications from a fall accounted for 10% of deaths ^[3] in one caregiver interview study. Falls lead to hip fractures (especially femoral neck fractures in osteoporotic elderly patients), head injuries (subdural haematoma, traumatic brain injury), and immobility complications (DVT/PE, pressure ulcers, deconditioning, pneumonia).

Repeated falls are a supportive clinical feature of DLB ^[2]^[4] — they are not just a complication but also part of the disease phenotype. However, each fall carries the risk of catastrophic secondary injury.

Prevention: Physiotherapy, occupational therapy home assessment, lying-standing BP monitoring, medication review (reduce sedatives, adjust antihypertensives), appropriate footwear, assistive devices, hip protectors.

This is the most clinically important preventable complication of DLB.

Antipsychotic sensitivity (30–50%): acute irreversible parkinsonism, LOC ± NMS towards antipsychotics ^[2]^[4]

Feature	Explanation
What happens	Administration of a dopamine-blocking antipsychotic (especially typical agents) to a DLB patient causes a dramatic, often irreversible worsening of parkinsonism, altered consciousness, and potentially neuroleptic malignant syndrome (NMS)
Why DLB is vulnerable	DLB patients already have severely depleted striatal dopamine due to nigrostriatal degeneration. Adding a D2 blocker removes the residual dopaminergic tone entirely → catastrophic motor and consciousness failure
NMS features	Hyperthermia, severe rigidity ("lead-pipe"), altered consciousness, autonomic instability (labile BP, tachycardia), elevated CK (rhabdomyolysis)
Irreversibility	Unlike drug-induced parkinsonism in a non-DLB patient (which usually reverses on drug withdrawal), the parkinsonism triggered by antipsychotics in DLB may be permanent because the underlying neuronal substrate is already critically damaged
Common clinical scenario	DLB patient presents with delirium or psychosis → treated with haloperidol in ED or ward → develops severe rigidity, LOC, and/or NMS within hours to days

Iatrogenic Disaster – The Most Dangerous Complication of DLB

Earlier diagnosis of DLB may prevent iatrogenic complications ^[3]. The single most important thing you can do for a DLB patient is to ensure that typical antipsychotics are NEVER prescribed. This requires clear documentation in the medical record, drug allergy alerts, and education of all members of the care team (including ED, nursing, and on-call doctors who may not know the patient).

6. Psychiatric Complications

Complication	Mechanism	Consequences
Severe orthostatic hypotension	Cardiac sympathetic denervation + loss of baroreceptor reflex	Syncope → falls → fractures → head injuries; cerebral hypoperfusion → worsening cognition
Constipation / bowel obstruction	Enteric α-synuclein → ↓GI motility	Severe constipation → faecal impaction → overflow diarrhoea (often mistaken for true diarrhoea) → delirium trigger; rarely, bowel obstruction or perforation
Urinary retention / incontinence	Sacral autonomic plexus dysfunction	UTI (from retention → stasis → bacterial colonisation) → delirium → further cognitive decline; social embarrassment → isolation
Cardiac arrhythmias	Cardiac autonomic denervation + QTc prolongation from medications	Sudden cardiac death (rare but reported)

Treatment	Potential Complication	Mechanism
Levodopa	Worsening hallucinations, psychosis, nausea, orthostatic hypotension	Dopaminergic stimulation of mesolimbic pathway → psychosis; peripheral dopamine effects → nausea, ↓BP
AChE inhibitors	GI side effects (nausea, diarrhoea, anorexia), bradycardia, syncope, vivid dreams	Cholinergic excess: GI (↑peristalsis, ↑secretion); cardiac (vagotonic → ↓HR); CNS (↑REM activity)
Clonazepam	Falls, cognitive impairment, respiratory depression in OSA	GABA-A potentiation → CNS depression, muscle relaxation, respiratory drive ↓
Antipsychotics (if used)	Neuroleptic sensitivity, NMS ^[2]^[4]	As described above — even quetiapine at higher doses can occasionally cause problems
Fludrocortisone	Supine hypertension, oedema, hypokalaemia	Mineralocorticoid effect → Na+/H₂O retention → volume expansion
Midodrine	Supine hypertension, urinary retention	α1-agonism → vasoconstriction (systemic, including splanchnic and bladder neck)

DLB progresses faster than Alzheimer disease. Survival approximately 5–8 years from symptom onset ^[3]. Average lifespan 7.7 years ^[4].

Most common causes of death ^[3]:

Cause	Percentage	Mechanism
Failure to thrive	65%	Terminal decline: progressive inability to eat, drink, move, or engage
Pneumonia and swallowing difficulties	23%	Aspiration pneumonia from oropharyngeal dysphagia; silent aspiration
Other medical conditions	19%	Cardiovascular events, infections, comorbidities
Complications from a fall	10%	Hip fracture → immobility → PE / pneumonia; traumatic brain injury

DLB progresses faster than Alzheimer disease, with the most common cause of death being failure to thrive, followed by pneumonia and swallowing difficulties, other medical conditions, and complications from a fall ^[3]

Frequently occurring copathology, most commonly with Alzheimer disease, leads to greater cognitive decline, increased likelihood of admission to a long-term care facility, and a higher risk of mortality ^[3]

50% of DLB patients have concomitant AD pathology (amyloid plaques, neurofibrillary tangles)
Copathology accelerates the rate of cognitive and functional decline
Patients with DLB + AD copathology lose memory functions earlier (because the AD pathology targets hippocampus) and progress to severe dementia more rapidly
Other copathologies (TDP-43, cerebrovascular disease) further contribute to accelerated decline

High Yield Summary — Complications of DLB

Failure to thrive is the most common cause of death (65%) — represents terminal decline from cumulative neurodegenerative burden ^[3]
Aspiration pneumonia (23% of deaths) — from progressive oropharyngeal dysphagia due to brainstem and pharyngeal motor involvement ^[3]
Falls and fall-related complications (10% of deaths) — from parkinsonism, orthostatic hypotension, fluctuations, and visuospatial deficits ^[3]
Neuroleptic sensitivity reactions (30–50%) — the most important PREVENTABLE complication; typical antipsychotics → acute irreversible parkinsonism, LOC, NMS ^[2]^[4]
Superimposed delirium — DLB patients are highly vulnerable (25% vs 7% in AD); each episode may cause permanent cognitive step-down ^[3]^[14]
AD copathology in > 50% → greater cognitive decline, institutionalisation, and mortality ^[3]
Prognosis: 5–8 years survival, average 7.7 years — faster than AD ^[3]^[4]
Caregiver burden in DLB is higher than in any other dementia subtype — address caregiver wellbeing, advance care planning, and timely palliative care referral ^[3]

Active Recall - Complications of DLB

References

^[2] Senior notes: Ryan Ho Neurology.pdf (Section 5.4.5 DLB, p.134) ^[3] Lecture slides: GC 241. Reference (3) - Patel dementia with lewy bodies.pdf ^[4] Senior notes: Ryan Ho Psychiatry.pdf (Section 4.2.5 DLB, p.95) ^[14] Medicine lecture slides: Delirium in Elderly People_Lancet.pdf

High Yield Summary

Dementia with Lewy Bodies (DLB) — Key Points for Exams

Second most common degenerative dementia after AD (4–30%) ^[2]^[4]
Pathology: Lewy bodies (phosphorylated α-synuclein) in deep cortical layers, brainstem, and peripheral autonomic system ^[2]^[4]
AD copathology in ≥ 50% of DLB cases ^[3]
Cognitive profile: early attention, executive, visuospatial deficits; memory affected LATE ^[2]^[4]
Core features (need ≥ 2 for probable DLB): (1) Cognitive fluctuations, (2) Visual hallucinations, (3) RBD, (4) Parkinsonism ^[2]^[4]
1-year rule: DLB = dementia before/within 1yr of parkinsonism; PDD = dementia > 1yr after established PD ^[1]^[2]^[3]
Antipsychotic sensitivity is life-threatening — NEVER give typical antipsychotics ^[2]^[4]
MRI: preserved medial temporal lobe (cf AD) ^[2]
SPECT/PET: occipital hypoperfusion (cf posterior temporal-parietal in AD) ^[2]^[5]
Three prodromal syndromes: MCI-Lewy, delirium-onset, psychiatric-onset ^[3]
Survival: 5–8 years from symptom onset (shorter than AD) ^[3]
Genetics: mostly sporadic; GBA mutation is strongest sporadic RF; SNCA duplication/triplication in familial cases ^[2]^[3]
Profound cholinergic deficit → good response to AChE inhibitors ^[1]^[2]

High Yield Summary – Differential Diagnosis of DLB

PDD vs DLB: Use the 1-year rule — dementia before/within 1yr of parkinsonism = DLB; dementia > 1yr after PD = PDD. DAT-SPECT cannot differentiate the two ^[3].
AD vs DLB: DLB = attention/executive/visuospatial early, memory late, VH early, RBD, parkinsonism, preserved medial temporal lobes, occipital hypoperfusion. AD = memory early (encoding), no VH/RBD/parkinsonism early, hippocampal atrophy. DAT-SPECT is most helpful for distinguishing DLB from AD ^[3].
Delirium vs DLB: Acute onset + identifiable precipitant = delirium. DLB fluctuations are chronic and without acute systemic cause. DLB patients are prone to delirium (25% vs 7% AD) — always rule out superimposed delirium ^[3].
NPH: Triad of gait apraxia + incontinence + dementia; no psychiatric symptoms, sleep disorder, or dysautonomic features; potentially reversible with VP shunt ^[2]^[4].
Parkinson-plus: MSA (dysautonomia + cerebellar), PSP (vertical gaze palsy + axial rigidity), CBD (asymmetric apraxia + alien limb) — all lack the VH/RBD/fluctuation triad of DLB ^[1].
Psychiatric-onset DLB: May mimic late-onset psychosis or depression — always screen for core DLB features before prescribing antipsychotics ^[3].
Two of every three DLB cases are missed or misdiagnosed ^[3] — maintain high clinical suspicion.

High Yield Summary — Diagnostic Criteria and Investigations for DLB

2017 McKeith Criteria: Required = progressive cognitive decline with functional impairment. 4 core features: fluctuations, VH, RBD, parkinsonism. ≥ 2 core features = probable DLB; 1 core + 1 indicative biomarker = probable DLB ^[3].
Three indicative biomarkers: reduced DAT uptake (SPECT/PET), low MIBG cardiac uptake, PSG-confirmed RSWA ^[3].
Three supportive biomarkers: preserved MTL on MRI, occipital hypometabolism on FDG-PET/SPECT (with posterior cingulate island sign), posterior EEG slowing ^[3].
DAT-SPECT is most helpful for distinguishing DLB from AD ^[3] — normal DAT argues against DLB.
MoCA preferred over MMSE because it tests executive and visuospatial domains more thoroughly ^[3].
α-Synuclein SAA (CSF) and skin biopsy confirm α-synucleinopathy but are NOT specific for DLB vs PD/PDD ^[3].
AD copathology in > 50% of DLB — consider AD biomarkers (CSF Aβ/p-tau, amyloid PET) ^[3].
EEG: posterior slowing < 8 Hz in ~90% DLB vs ~10% AD — highly discriminative ^[3].
Always screen for reversible causes of dementia: TFT, B12, folate, syphilis, calcium, glucose ^[2].

High Yield Summary — Management of DLB

No disease-modifying therapy available — all treatment is symptomatic ^[2]^[3]^[4]
Step 1: Comprehensive medication review — stop anticholinergics, antihistamines, OTC sleep aids (diphenhydramine), typical antipsychotics ^[3]
Step 2: Non-pharmacological interventions — cognitive stimulation, bedroom safety for RBD, fall prevention, caregiver education, advance care planning
Cognition + VH: AChE inhibitors are first-line (donepezil, rivastigmine, galantamine) — work better in DLB than AD due to more severe cholinergic deficit ^[2]^[4]
Psychosis (severe BPSD only): very low-dose quetiapine or clozapine only — NEVER typical antipsychotics ^[2]^[4]^[12]
RBD: melatonin first-line, clonazepam second-line ^[4]^[12]
Parkinsonism: levodopa-carbidopa — avoid dopamine agonists (worsen hallucinations) ^[2]^[4]^[12]
Depression: SSRIs — avoid TCAs (anticholinergic) ^[2]^[4]
Autonomic: avoid anticholinergic bladder drugs — use mirabegron for urinary symptoms, fludrocortisone/midodrine for orthostatic hypotension
Prognosis: 5–8 years survival; faster progression than AD ^[3]^[4]
Advance care planning is essential — discuss early with patient and family ^[3]

High Yield Summary — Complications of DLB

Failure to thrive is the most common cause of death (65%) — represents terminal decline from cumulative neurodegenerative burden ^[3]
Aspiration pneumonia (23% of deaths) — from progressive oropharyngeal dysphagia due to brainstem and pharyngeal motor involvement ^[3]
Falls and fall-related complications (10% of deaths) — from parkinsonism, orthostatic hypotension, fluctuations, and visuospatial deficits ^[3]
Neuroleptic sensitivity reactions (30–50%) — the most important PREVENTABLE complication; typical antipsychotics → acute irreversible parkinsonism, LOC, NMS ^[2]^[4]
Superimposed delirium — DLB patients are highly vulnerable (25% vs 7% in AD); each episode may cause permanent cognitive step-down ^[3]^[14]
AD copathology in > 50% → greater cognitive decline, institutionalisation, and mortality ^[3]
Prognosis: 5–8 years survival, average 7.7 years — faster than AD ^[3]^[4]
Caregiver burden in DLB is higher than in any other dementia subtype — address caregiver wellbeing, advance care planning, and timely palliative care referral ^[3]

Dementia With Lewy Bodies

Dementia with Lewy Bodies (DLB)

4. Anatomy and Function (Relevant Neuroanatomy)

5. Aetiology and Pathophysiology

6. Classification

7. Clinical Features

7.2 Core Clinical Features

8. Clinical Approach to a Patient with Suspected DLB

Active Recall - Dementia with Lewy Bodies (Clinical Features & Pathophysiology)

Differential Diagnosis of Dementia with Lewy Bodies

Detailed Differentials

Active Recall - Differential Diagnosis of DLB

References

Diagnostic Criteria, Algorithm, and Investigations for Dementia with Lewy Bodies

1. Diagnostic Criteria — 2017 Revised McKeith Criteria (Fourth Consensus Report)

3. Investigations — Modalities, Key Findings, and Interpretation

3.3 Structural Neuroimaging

3.4 Functional Neuroimaging

3.7 Synuclein-Specific Markers (Emerging Biomarkers)

Active Recall - DLB Diagnostic Criteria and Investigations

References

Management of Dementia with Lewy Bodies

Detailed Treatment Modalities

2. Non-Pharmacological Interventions

3. Pharmacological Treatment — By Symptom Domain

3.1 Cognition and Neuropsychiatric Symptoms

Active Recall - Management of DLB

References

Complications of Dementia with Lewy Bodies

6. Psychiatric Complications

Active Recall - Complications of DLB

References

On this page

Dementia With Lewy Bodies

1. Definition

2. Epidemiology

3. Risk Factors

4. Anatomy and Function (Relevant Neuroanatomy)

4.1 Sites of Lewy Body Deposition and Functional Correlates

4.2 Key Neurotransmitter Deficits

5. Aetiology and Pathophysiology

5.1 The Central Pathological Event: α-Synuclein Misfolding and Aggregation

5.2 Copathology

5.3 Genetic Basis

6. Classification

6.1 Within the Lewy Body Dementia Spectrum

6.2 Prodromal DLB Syndromes

6.3 Diagnostic Certainty Classification (2017 Revised McKeith Criteria)

7. Clinical Features

7.1 Cognitive Profile (the Dementia Itself)

7.2 Core Clinical Features

7.2.1 Cognitive Fluctuations (60–80%)

7.2.2 Recurrent Visual Hallucinations (67%)

7.2.3 REM Sleep Behaviour Disorder (RBD) (85%)

7.2.4 Spontaneous Parkinsonism (70–90%)

7.3 Supportive Clinical Features

7.4 Autonomic Features (Expanded)

7.5 Summary: Symptoms vs Signs

7.6 Comparison with Other Common Dementias

8. Clinical Approach to a Patient with Suspected DLB

Key History Points to Elicit

Physical Examination Focus

Active Recall - Dementia with Lewy Bodies (Clinical Features & Pathophysiology)

References

Why Is the Differential Diagnosis of DLB Challenging?

Differential Diagnosis Decision Framework

Detailed Differentials

1. Parkinson's Disease Dementia (PDD)

2. Alzheimer Disease (AD)

3. Delirium

4. Frontotemporal Dementia (FTD)

5. Vascular Dementia (VaD)

6. Normal Pressure Hydrocephalus (NPH)

7. Other Parkinson-Plus Syndromes

8. Primary Psychiatric Disorders (Late-Onset Psychosis, Depression)

9. Drug-Induced Parkinsonism

10. Non-Convulsive Status Epilepticus (NCSE)

11. Creutzfeldt-Jakob Disease (CJD)

Summary Comparison Table

Active Recall - Differential Diagnosis of DLB

1. Diagnostic Criteria — 2017 Revised McKeith Criteria (Fourth Consensus Report)

1.1 Essential (Required) Feature

1.2 Core Clinical Features

1.3 Supportive Clinical Features

1.4 Indicative Biomarkers

1.5 Supportive Biomarkers

1.6 Diagnostic Certainty Classification

1.7 MCI Due to Lewy Bodies (Research Criteria)

2. Diagnostic Algorithm

3. Investigations — Modalities, Key Findings, and Interpretation

3.1 Bedside Cognitive Assessment

3.2 Fluctuation Assessment Scales

3.3 Structural Neuroimaging

CT Brain

MRI Brain

3.4 Functional Neuroimaging

Dopamine Transporter SPECT/PET (DAT Scan) — Indicative Biomarker

Cerebral Perfusion SPECT / FDG-PET — Supportive Biomarker

MIBG Myocardial Scintigraphy — Indicative Biomarker

3.5 Polysomnography (PSG) — Indicative Biomarker

3.6 EEG — Supportive Biomarker

3.7 Synuclein-Specific Markers (Emerging Biomarkers)

α-Synuclein Seed Amplification Assay (SAA) — CSF

α-Synuclein Skin Biopsy

3.8 AD Biomarkers (To Assess Copathology)

3.9 Routine Bloods (Exclude Reversible Causes)

3.10 Summary Table — All Investigations in DLB

4. Putting It All Together — Clinical Reasoning

Active Recall - DLB Diagnostic Criteria and Investigations

Overarching Principles

Management Algorithm

Detailed Treatment Modalities

1. Medication Review — What to Stop